This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Electrical signaling in the brain and heart is driven by the action of ion channel proteins. These proteins from holes in the cell membrane that open and close to allow the passage of ions such as calcium and potassium. We are investigating the structures and functions of a range of ion channels, ion channel regulatory proteins, and transporters. The goals are to uncover the basic biophysical mechanisms by which these transmembrane proteins work, to understand their structures and interactions in atomic detail, and to understand how their functions are compromised in human diseases such as cardiac arrhythmias, epilepsy, deafness, and mental illness.For our research it is essential to know the molecular identity of the proteins and protein fragments that we study. Mass spectrometry provides the most accurate way to make these molecular identifications.